1. Field of the Invention
The present invention relates to a digital video disc-random access memory (DVD-RAM) and a digital video disc-recordable/rewritable (DVD-R/RW), and more particularly, to a digital modulation apparatus used with a DVD-RAM and a DVD-R/RW and a method thereof. The present application is based on Korean Patent Application 2001-42819, filed Jul. 16, 2001, which is incorporated herein by reference.
2. Description of the Related Art
A digital modulation and demodulation apparatus is used to record data on optical disc media such as DVD-RAMs and DVD-R/RWs, or to reproduce data from an optical disc media. As shown in FIG. 1, a conventional digital modulation and demodulation apparatus includes a modulation unit 11 for modulating user data, that is, data words D(i) (where i is an integer), into a non-return-to-zero inverted (NRZI) signal SNRZI, an optical head 13 for writing a NRZI signal SNRZI to an optical disc 17 and reading the NRZI signal SNRZI from the optical disc 17, and a demodulation unit 15 for demodulating the NRZI signal SNRZI read from the optical disc 17 into original data words D(i).
In particular, in the modulation unit 11, the data words D(i) are converted by a code converter 11a into code words C(i), and the converted code words C(i) are converted by a NRZI converter 11b into the NRZI signal SNRZI. Eight-to-fourteen modulation (EFM) conversion, or eight-to-fourteen modulation plus (EFMplus) conversion is used to convert the data words D(i) into the code words C(i) through the code converter 11a. EFMplus conversion is an improved EFM conversion method for high-density recording and improving performance.
In the demodulation unit 15, the NRZI signal SNRZI, read from the optical disc 17, is converted by a reversed NRZI converter 15a into the code words C(i), and the reversed-converted code words C(i) are reversed-converted by a reversed code converter 15b into the original data words D(i).
FIG. 2 is a detailed block diagram of a modulation unit shown in FIG. 1. Here, a case where the EFMplus conversion method is used is shown.
Referring to FIG. 2, the modulation unit 11 includes a data fetch and sync code generation unit 21, an EFMplus converter 23, a NRZI converter 25, and a first-in first-out (FIFO) buffer 27.
The data fetch and sync code generation unit 21 fetches input user data, that is, 8-bit data words D(7:0), generates 16-bit sync codes S(15:0) and outputs the 8-bit data words D(7:0) and the 16-bit sync codes S(15:0).
The EFMplus converter 23 receives the 8-bit data words D(7:0) and the 16-bit sync codes S(15:0), performs eight-to-sixteen modulation (ESM), checks a digital sum value (DSV) and runlength limits (RLL) and outputs 16 bit-converted code words C(15:0). The NRZI converter 25 converts the 16 bit-converted code words C(15:0) into the NRZI signal SNRZI. The NRZI signal SNRZI is output as 1-bit serial data S′NRZI through the FIFO 27.
However, in the conventional modulation apparatus shown in FIG. 2, data processing is sequentially performed, and thus, internal delay may increase. In this case, the margin of an operation of external devices such as a write strategy control (WSC) apparatus and an optical pick-up apparatus, may not be enough. Further, in the conventional modulation apparatus, the 8-bit data words D(7:0) are directly converted into the 16-bit code words C(15:0), and thus, the size of the conventional modulation apparatus may increase in a case where the conventional modulation apparatus is implemented with integrated circuits. Further, the conventional modulation apparatus is constituted to be used only for one of a DVD-RAM and a DVD-R/RW.